I started using my iPhone's Notes app for private conversations. Here's how.

How to add a password to Notes on iPhone/iPad Here’s how to set up a password that can be used to lock and unlock individual Notes.

By opening a new note on an iPhone and sharing it with people of your choosing, they'll not only be able to view your note, but also edit and update, all in real time.

You can change your Notes settings on your iPhone using the Settings app. Changes include how notes display and how lists sort in the app.